The present invention relates to a cutting tool insert coated with a hard and wear resistant coating comprising a nanolaminated structure based on (Ti,Al)N and (Ti,Si)N layers, respectively. This insert is particularly useful in metal cutting applications generating high temperatures, e.g., machining of super alloys, stainless steels and hardened steels. The coating is grown by physical vapour deposition (PVD) and preferably by cathodic arc evaporation.
U.S. Pat. No. 7,056,602 discloses a cutting tool insert coated with a cubic structured (TiyAlxMe1-x-y)N based layer where Me is one of the elements: Zr, Hf, V, Nb, Ta, Cr, Mo, W or Si, and: x is between 0.50 and 0.80; the ratio, x/(x+y), is between 0.50 and 0.85; the sum of Ti and Al subscripts, x+y, is between 0.7 and 1.0.
EP 1736565 discloses a cutting tool cubic boron nitride based insert coated with a cubic structured (Me,Si)X phase, where Me is one or more of the elements Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and Al, and X is one or more of the elements N, C, O or B
EP 0588350 discloses a hard layer of Ti—Si—N composite material on a body, the layer being deposited using a source of evaporation possessing a composition of TiaSib with a in the range of 75-85 at % and b 15-25 at %.
Coating optimization has also been obtained by applying different concepts of multilayers as; alternating Ti and Al containing layers (U.S. Pat. No. 6,309,738), oxygen and non-oxygen containing layers (U.S. Pat. No. 6,254,984), one of the layers stacked in the multilayer consists itself of a multilayer (U.S. Pat. No. 6,077,596), alternating nitrogen content (U.S. Pat. No. 5,330,853) or using one metastable compound (U.S. Pat. No. 5,503,912) or as aperiodic multilayer (U.S. Pat. No. 6,103,357).
Further improvements in thermal stability and hardness have been achieved by the introduction of Si into TiN- or TiAlN-based coatings. JP 2000-334607 discloses a coated tool with laminated layers comprising TiSi (layer a) and TiAl (layer b) compounds. The (a) layer is selected among nitride, carbonitride, oxynitride and oxycarbonitride containing 10%<Si<60% with a NaCl type crystalline structure. Layer (b) is selected among nitride, carbonitride, oxynitride and oxycarbonitride containing 40%<Al<75% with a NaCl type crystalline structure. The (a) layer and (b) layers are applied alternately and the (b) layer is located just above the surface of the base material.
EP 1939327 discloses a cutting tool comprising a hard coating giving improved crater and flank wear resistance, said coating comprising an aperiodic multilayer X+Y+X+Y+ . . . with average layer thickness of X and Y layers of between 0.1 and 100 nm and with average chemical composition AlaTibSicCrdCeN1-e, where 0<a<0.5, 0.1<b<0.9, 0.01<c<0.17, 0≦d<0.06, a+b+c+d=1, and 0≦e<1.
The trends towards dry-work processes for environmental protection, i.e., metal cutting operation without using cutting fluids (lubricants) and accelerated machining speed with improved process put even higher demands on the characteristics of the tool materials due to an increased tool cutting-edge temperature. In particular, coating stability at high temperatures, e.g., oxidation- and wear-resistance have become even more crucial.